1. Field of the Invention
This invention relates generally to a method and apparatus to controllably create controlled necrosis of at least a portion of the uterus, and more particularly to a method and apparatus to create selective cell necrosis of target sites of the uterus.
2. Description of Related Art
There are a number of body organs and lumens, including but not limited to the uterus, gall bladder, large intestine and the like, that have inner layers that develop disease states or otherwise abnormal conditions which can cause discomfort to the patient and are precursors to disease states. Traditional methods of treatment for these conditions have included removal all or a major portion of the body organ (e.g. hysterectomy).
Menorrhagia an abnormality of the uterus, is an example of such a disease state. It is characterized by excessive menstrual bleeding of the endometrium in the absence of organic pathology. While the disease has no known aetiology, it has been postulated that it is due to an inappropriate exposure of the endometrium to hormones. Approximately 10% of all women in the US experience menorrhagia and it is responsible for approximately one in five outpatient referrals to gynecological departments. At a minimum, the disease can cause considerable discomfort, distress and curtailment of lifestyle. Women suffering severe menorrhagia are at risk from chronic anemia and other complications. Moreover, it is the most frequent clinical indication for hysterectomy.
While there are a number of available treatments for the disease, many have limitations and/or potentially adverse complications. For example, currently available pharmacological therapy requires the long term administration of medication, which in some case provides only temporary beneficial effects while presenting potentially long term adverse side effects. Hysterectomy is another common treatment, but the associated morbidity and convalescence period can be prolonged, making this treatment an undesirable choice for some patients.
A number of physical and chemical methods have been tried as alternatives to hysterectomy, including the use of superheated steam, cryotherapy, urea injection and radium packing. The most commonly used methods as an alternative to hysterectomy are, ablation of the endometrium either by using a laser, such as a Nd:YAG laser, or the use of RF energy applied with an electrode.
Laser treatments have provided only limited success. RF is an attractive alternative. In RF heating, a conductive probe is placed within the uterine cavity and an insulated ground-plane electrode or belt is placed around the patient's midriff. RF energy is applied to the thermal probe with the external belt electrode acting as the return arm of the circuit. The electrical load presented by the RF thermal probe, patient, and external belt is matched to the output of the RF generator via a tuning unit, to form a series resonant circuit. Once tuned, the majority of the power applied to the probe is deposited into the endometrium as heat.
Current flows primarily capacitively, and an electric field is set up around the active tip of the probe. Tissue lying within the field becomes heated because of rapid oscillation of charged particles and locally induced currents.
Prior et al. have reported on the use of RF to treat menorrhagia. Power at 27.multidot.12 MHz was delivered to a probe that was placed into the uterine cavity and capacitively coupled to a second electrode consisting of a belt placed around the patient (Prior et al., Int. J. Hyperthermia, 1991, Vol. 7, No. 2, pgs. 213 to 220). The active electrode was a 10 mm diameter stainless-steel cylinder with a length of 70 mm. This method, however, did not adequately deliver RF energy to the entire endometrium. Because the endometrium has an irregular surface, it is difficult to deliver sufficient RF energy to the entire structure and effectively treat menorrhagia.
However, it is desirable to have close contact between the RF conductive face and the endometrium. In U.S. Pat. No. 5,277,201 (the "'201 patent") an electroconductive, expandable balloon expands the interior of the uterus and effects electrical contact with the endometrial lining to be destroyed. The device of the '201 patent fails, however, to provide sufficient physical contact with the entire endometrium, and thus the treatment is not complete. Not only is the physical contact with the endometrium unsatisfactory, but the effective delivery of RF energy to the endometrium could be improved as well.
There is a need to provide a method and apparatus to minimally invasively treat the uterus. There is a another need for a method and apparatus to minimally invasively treat selected sites of the uterus. There is a further need for a method and apparatus to selectively treat endometriosis and/or fibroids. There is yet another need for a method and apparatus to deliver sufficient energy to treat a substantial portion of the uterus.